Monday, March 10, 2008

Monkey chat sheds light on evolution of syntax

Much of the power of language comes from syntax, which lets you combine the same signal elements in different ways to get different meanings. For instance, "Bob outran the tiger" conveys a rather different outcome than "The tiger outran Bob".

But how did syntax evolve? One standard explanation is that syntax arises when the vocabulary of signals gets so large that it becomes easier to combine signals in new ways than to make new signals.

But now it appears that syntax can arise from the other end of the signal-complexity spectrum, as well. Kate Arnold and Klaus Zuberbühler of the University of St. Andrews, UK, have been studying communication in putty-nosed monkeys, a social primate that lives in the forests of Nigeria.

In their alarm calls, the monkeys have a vocal repertoire of just two syllables, "pyow" and "hack". A series of hacks alerts the group that an eagle is nearby, while pyows warn of a leopard. But the monkeys eke a third meaning from the two calls by putting them together into a pyow-hack call that means "let's move along".

Listen to "hacks"

"pyows"

and "pyow-hacks"

Earlier work by Arnold and Zuberbühler had documented all three meanings, but left open the possibility that the "pyows" and "hacks" in the pyow-hack differed subtly from their solo counterparts. Now that possibility has been ruled out.

The pair synthesised artificial "pyow-hack" by combining "pyows" and "hacks". Sure enough, when they played these calls to real monkeys, they still understood it was time to move on. (Current Biology, vol.18, p.202)

Two signals, three meanings. Not a very sophisticated syntax, admittedly - but it's a start.Bob Holmes, New Scientist correspondent